1. Field of the Invention
The present invention relates generally to a device for securing a protective sleeve onto a core exit thermocouple instrumentation (xe2x80x9cCETxe2x80x9d) column. More particularly, the present invention relates to a locking sleeve coupled to a reactor instrumentation protective sleeve, wherein the locking sleeve covers at least a portion of a clip assembly that couples the protective sleeve to the CET column.
2. Description of Related Art
During the assembly and reassembly of a commercial pressurized water reactor nuclear reactor vessel, it is necessary to protect the CET instrumentation leads. To provide this protection, these instrumentation leads are typically housed in a protective sleeve, conventionally known in the art as a xe2x80x9cbullet nose assembly.xe2x80x9d This protective sleeve is secured such that it is not removed with the reactor closure during disassembly. Typically the protective sleeve is secured to the CET instrumentation column using either a retaining ring or a spring-loaded C-shaped clip hinged at one end and selectively operable and closeable at the opposite end.
FIG. 1 shows and example of a prior art device. The locking device 1 includes a protective sleeve 2, a retaining ring or clip assembly 4 and a CET column 6.
The protective sleeve 2 is a cylindrically shaped member having an open center. The protective sleeve 2 also includes an annular groove 3 in its outer periphery. The annular groove 3 includes one or more apertures (not shown). The protective sleeve 2 is typically constructed from several open center cylindrical elements welded together to form the protective sleeve.
As seen in FIG. 1, the CET column 6 is a cylindrically shaped element having first and second ends. The first end (not shown) is fastened to the reactor vessel internals approximately ten feet below the protective sleeve 2. The second end 8 is the exit point for the CET instrumentation leads 7.
The CET instrumentation leads 7 are typically a plurality of 12 or 13 tubes containing CETs that extend vertically from a horizontal plane near the top of the CET column 6. The instrumentation leads 7 extend approximately 1 to 4 feet vertically above the second end 8 of the CET column 6. The lengths of the instrumentation leads 7 for a particular CET column 6 are staggered in this length range to permit the reception of the protective sleeve 2. These instrumentation leads 7 are terminated with electrical connectors (not shown). For installation of the protective sleeve 2, it is necessary to disconnect the instrumentation leads 7 from their associated field cabling.
The protective sleeve 2 has two ends. One end has an open center that first receives the disconnected instrumentation leads 7 and then the fixed diameter of the CET column 6. This end of the protective sleeve is where the retaining ring or clip assembly 4 is located. The other end of the protective sleeve 2 is terminated with a conical end fitting (not shown). This conical end fitting permits the protective sleeve 2 to be received by the reactor vessel closure during reactor reassembly. The overall length of the protective sleeve 2 is sized such that the instrumentation leads 7 can be received and housed by the open center of the protective sleeve 2 without being vertically challenged.
The retaining ring or clip assembly 4 couples the protective sleeve 2 and the CET column 6 together. The retaining ring or clip assembly 4 may be a spring-loaded C-shaped member having two legs hingedly coupled together and the free ends releasably joined together. Typically, a mechanical fastener such as a spring-loaded detent is used to join the free ends of the clip.
In a conventional set up, the retaining ring or clip assembly 4 is installed in the annular groove 3 defined by the protective sleeve 2 so as to mechanically engage the CET column 6. This arrangement locks the protective sleeve 2 in position on the CET column 6.
Undesirable mechanical interferences, debris or other objects falling onto the retaining ring or clip assembly 4 may cause the spring-loaded detent to become disengaged from the protective sleeve 2. The disengagement of the retaining ring or clip assembly 4 from the protective sleeve 2 may result in significant damage to the instrumentation leads, increased radiation exposure to personnel involved with the evaluation and repair of the instrumentation leads and significant delays in outage evolution. The resultant evaluations, delays and repair work alone may add hundreds of thousands of dollars to reactor maintenance costs.
Additionally, the retaining ring or clip assembly 4 is small enough that it may fall into the reactor vessel, thus, resulting in the introduction of foreign material into the reactor vessel internals. All foreign material is closely monitored and must be removed from the internal of the reactor vessel to avoid significant damage to the operating system.
Finally, the existing protective sleeve 2 design permits installation of the retaining ring or clip assembly 4 onto the CET column 6 in only one orientation. In some instances, the retaining ring or clip assembly 4 has been installed in an orientation that prevents it from fully engaging the CET column 6. This lack of full engagement may result in disengagement of the retaining ring or clip assembly 4 from the protective sleeve 2, resulting in significant damage to the operating system.
Therefore, there is needed a locking device which permits the retaining ring or clip assembly 4 to be installed in a plurality of orientations and which helps maintain the retaining ring or clip assembly 4 in the locked position until intentionally disengaged.
This invention relates to a locking device. In the preferred embodiment, the locking device is used in a nuclear power plant to provide a barrier surface over a clip assembly used to couple the protective sleeve to a core exit thermocouple column.
The locking device includes a protective sleeve and a locking sleeve supported by the protective sleeve. The protective sleeve defines an annular groove in the outer periphery thereof having apertures alternately spaced between vertically extending fingers. The protective sleeve also includes threads supported by its outer periphery.
The protective sleeve is received over the CET column to help prevent damage to the CET column instrumentation leads. A clip assembly is used to couple the protective sleeve to the CET column.
The clip assembly includes two legs hingedly coupled together at one end and releasably joined at the opposite end. Each leg supports at least one inwardly projecting raised surface contoured to engage an annular groove in the outer periphery of the CET column. During installation, the clip assembly is received in the annular groove defined by the protective sleeve.
The locking sleeve is a cylindrically shaped member, and is received over the clip assembly. The locking sleeve is coupled to the protective sleeve such that it covers at least a portion of the protective sleeve. The locking device includes threads supported by the internal surface thereof for mating with the threads of the protective sleeve.
In another embodiment, the invention relates to a locking device for a reactor instrumentation protection sleeve and instrumentation column assembly joined by a selectively openable and closable clip. The locking device includes a protective sleeve having an elongated body supporting a first set of threads on at least a portion of the outer perimeter thereof and a locking sleeve having an elongated body supporting a second set of threads on the interior surface thereof for mating with the first set of threads, whereby the locking sleeve is adapted to cover at least a portion of the protective sleeve once the first set of threads and the second set of threads are engaged.
In still another embodiment, the combination of the locking device and an instrumentation column protective sleeve includes an instrumentation column; a protective sleeve surrounding the outer perimeter of a portion of the instrumentation column; a clip assembly supported by the protective sleeve, wherein the clip assembly couples the instrumentation column and protective sleeve together; and a locking sleeve supported by the protective sleeve, the locking sleeve being coupled to the protective sleeve such that the locking sleeve is adapted to cover at least a portion of the clip assembly and the protective sleeve.